Telecom quantum memory over one microsecond in nanophotonic lithium niobate

TL;DR

This paper demonstrates a nanophotonic quantum memory in erbium-doped lithium niobate that stores telecom-band photons for over a microsecond, verifying quantum coherence and multi-mode capacity, advancing on-chip quantum technologies.

Contribution

The authors present a practical, on-chip quantum memory platform using erbium-doped lithium niobate capable of long storage times and multi-mode operation at telecom wavelengths.

Findings

Stored single-photon-level pulses for over one microsecond.

Achieved an acceptance bandwidth of up to 2.2 GHz.

Demonstrated phase coherence and low noise in retrieval.

Abstract

Nanophotonic quantum memory is a vital component for scalable quantum information processing for quantum computing, networking, and sensing applications. We store single-photon-level telecom-band optical pulses for more than a microsecond using an atomic frequency comb in erbium-doped thin-film lithium niobate, well beyond what is practically feasible via propagation in even the best nanophotonic devices due to propagation losses. We verify the quantum nature of this storage by demonstrating the phase coherence and sub-single-photon noise upon retrieval. We also show the flexibility of our platform by storing up to 20 temporal modes and demonstrating an acceptance bandwidth up to 2.2 GHz. These results establish erbium-doped thin-film lithium niobate as a practical platform for on-chip quantum memory at telecom wavelengths, a key missing element for photonic quantum computing and quantum networking.